Factors influencing fluorescence spectra of free porphyrins.

1988 ◽  
Vol 34 (4) ◽  
pp. 757-760 ◽  
Author(s):  
C F Polo ◽  
A L Frisardi ◽  
E R Resnik ◽  
A E Schoua ◽  
A M Batlle
Keyword(s):  
Ionic Strength ◽  
Fluorescence Spectra ◽  
Emission Spectra ◽  
Main Peak ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Experimental Conditions ◽  
Organic Mixture ◽  
Carbonate Buffer ◽  
Factors Influencing

Abstract We recorded fluorescence excitation and emission spectra of uro- and coproporphyrin under different experimental conditions, to see how these conditions influence quantifications based on measurement of fluorescence intensity. We found that, for bands alpha and beta of the emission spectra and the main peak of the excitation spectra, fluorescence depends on pH and is minimal near pH 5 and near pH 7-7.5 for copro- and uroporphyrin, respectively. For band gamma of the emission spectra there was a constant decrease of fluorescence with increasing alkalinity of the solution. The intensity of porphyrin fluorescence also depends on ionic strength, reaching sharp maxima at 0.1 mol/L (for uroporphyrin) and 1 mol/L (for coproporphyrin). The organic mixture ethyl acetate:acetic acid (4:1 by vol), commonly used to extract porphyrins from biological samples, markedly diminishes the fluorescence of both porphyrins as compared with the same concentration of each porphyrin in aqueous acidic solvent. Furthermore, when we measured different ratios of uro:copro mixture at three distinct pHs and buffers, we found that at pH 10.5 (in carbonate buffer) the measured units of fluorescence depend only on total porphyrin concentration and not on the composition of the mixture.

scholarly journals Electronic Spectra of 1-Phenylethylamine and its Derivatives in Supersonic Jets

1990 ◽  
Vol 10 (3) ◽  
pp. 169-175
Author(s):  
Seiji Yamamoto ◽  
Taeko Niwa ◽  
Mitsuo Ito
Keyword(s):  
Relaxation Process ◽  
Electronic Spectra ◽  
Fluorescence Spectra ◽  
Phenyl Group ◽  
Nonradiative Relaxation ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Fluorescence Excitation Spectra ◽  
Dispersed Fluorescence ◽  
Asymmetric Carbon

The S1←S0 fluorescence excitation spectra and dispersed fluorescence spectra of jet-cooled (+)-, (-)- and (±)-1-phenylethylamine and their derivatives (amides) have been observed. The 0-0 band of the amine locates at 37,641 cm-1. The amides which were synthesized from (+)-amine or (-)-amine with (+)-tartaric acid are diastereomers. It was found that the two diastereomers give the identical spectra with the 0-0 band at 34,757 cm-1. No difference in the spectrum indicates that the excitation is localized in the phenyl group which is far from the asymmetric carbon causing diastereoism. It was also found that 1-phenylethylamine has a fast nonradiative relaxation process in the Sstate, but such a process is removed by the formation of the amide.

Fourier Transform Fluorescence Spectrometry

1988 ◽  
Vol 42 (8) ◽  
pp. 1563-1566 ◽  
Author(s):  
B. Hlivko ◽  
H. Hong ◽  
R. R. Williams
Keyword(s):  
Fourier Transform ◽  
Fluorescence Polarization ◽  
Fluorescence Spectra ◽  
Laser Excitation ◽  
Emission Spectra ◽  
Laser Fluorescence ◽  
Fluorescence Spectrometry ◽  
Excitation Spectra ◽  
Polarization Spectra ◽  
Monochromatic Source

A variety of fluorescence spectra have been measured interferometrically, demonstrating the feasibility of Fourier Transform Fluorescence Spectrometry (FT-FS). Emission spectra have been measured with the use of a monochromatic source and an interferometer as the emission selector. Excitation spectra have been measured with the use of a multi-line laser. Fluorescence polarization spectra have also been recorded with the use of laser excitation. The analytical characteristics of working curves are discussed.

Laser-induced fluorescence and discharge emission spectra of CrO. Rotational analysis of the A5Π–X5Π transition

1980 ◽  
Vol 58 (4) ◽  
pp. 516-533 ◽  
Author(s):  
W. H. Hocking ◽  
A. J. Merer ◽  
D. J. Milton ◽  
W. E. Jones ◽  
G. Krishnamurty
Keyword(s):  
Fluorescence Spectra ◽  
Rotational Temperature ◽  
Electronic States ◽  
Emission Spectra ◽  
Laser Induced Fluorescence ◽  
Spin Orbit Coupling ◽  
Excitation Spectra ◽  
Large Numbers ◽  
Parallel Polarization ◽  
Indirect Information

The A5Π–X5Π electronic transition of CrO, near 6000 Å, has been analysed in detail using laser-induced fluorescence and conventional discharge emission spectroscopy. The transition provides the first instance where it has been possible to analyse the rotational structures of quintet electronic states completely. Although the parallel polarization of the transition has prevented the spin–orbit coupling and Λ-doubling intervals from being observed directly, it is shown that sufficient indirect information exists in the spectrum for them to be obtained with fair precision. The excited state, A5Π, is perturbed by large numbers of other electronic states which have no intensity of their own for emission to the ground state. The analysis of the perturbed regions has been greatly facilitated by the laser-induced fluorescence spectra: the excitation spectra correspond to a rotational temperature close to room temperature (which offers a significant improvement in resolution over the discharge spectra), and the J-assignments of the perturbed lines given by the resolved fluorescence spectra are unambigious

Correction of Fluorescence Spectra

1994 ◽  
Vol 48 (4) ◽  
pp. 436-447 ◽  
Author(s):  
J. W. Hofstraat ◽  
M. J. Latuhihin
Keyword(s):  
Absorption Spectra ◽  
Wavelength Range ◽  
Fluorescence Spectra ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Wavelength Dependence ◽  
Excitation Spectra ◽  
Excitation Light ◽  
Radiative Processes ◽  
Sensing Applications

Several methods that can be applied to remove wavelength-dependent instrumental effects from fluorescence emission and excitation spectra have been investigated. Removal of such artifacts is necessary for the comparison of spectra that have been obtained on different instruments. Without correction, spectral line positions and relative intensities will be instrument-determined to a great extent. Furthermore, the application of adequate correction procedures provides excitation spectra which can be directly compared to absorption spectra; comparison of corrected excitation spectra and absorption spectra can be used to interpret the efficiency and pathways of radiative processes. Finally, corrected reflection spectra can be obtained, which can be directly transformed into absorption spectra and are useful for remote sensing applications. The methods that have been studied for the correction of emission spectra are the application of a standard lamp with calibrated spectral output and the use of fluorescence standards. The standards are a series of luminescent phosphors in polymer films and a solution of quinine sulfate dihydrate in perchloric acid, all provided with certified spectral emission values. For correction of excitation spectra, a quantum counter was applied. Several quantum counters were investigated. The best results were obtained for application of a mixture of the dyes basic blue and HITC, which provided good correction for the wavelength range 250 to 820 nm. No good quantum counters have been reported thus far for this (large) wavelength range. Correction for wavelength dependence of the excitation optics was realized by measurement of the excitation light intensity at the sample position and at the reference position with a Si photodiode. Correction factors for the excitation spectra were checked with a number of reference materials. Attention has also been paid to polarization-dependent effects that may occur in fluorescence spectra. The application of correction procedures was demonstrated for phytoplankton fluorescence spectra.

scholarly journals Optically Dilute, Absorbing, and Turbid Phantoms for Fluorescence Spectroscopy of Homogeneous and Inhomogeneous Samples

1993 ◽  
Vol 47 (12) ◽  
pp. 2114-2121 ◽  
Author(s):  
A. J. Durkin ◽  
S. Jaikumar ◽  
R. Richards-Kortum
Keyword(s):  
Optical Properties ◽  
Fluorescence Spectra ◽  
Flavin Adenine Dinucleotide ◽  
Emission Spectra ◽  
Hemoglobin Concentration ◽  
Scattering Coefficient ◽  
Polystyrene Microspheres ◽  
Fluorescence Excitation ◽  
Structure Boundary ◽  
Optical Properties Of Tissue

This paper presents a phantom which simulates the optical properties of tissue. The phantom absorption coefficient, scattering coefficient, anisotropy factor, and fluorescence quantum yield can be independently varied to investigate the effects of these parameters on fluorescence excitation and emission spectra from 300 to 650 nm. Phantom fluorophores include Flavin Adenine Dinucleotide (FAD) and Rhodamine B. Absorption is controlled by adjusting phantom hemoglobin concentration. On the basis of their smoothly varying scattering coefficient and the relatively low amount of fluorescence contributed to the mixture in comparison to other available scatterers, 1.05-µm-diameter polystyrene microspheres were selected as a scatterer. Sample inhomogeneities are simulated by preparing the phantom in a gelatin substrate. The optical properties of turbid phantoms determined with the use of indirect techniques agree well with known values as long as µs(l – g) > µa. Data are presented from dilute, absorbing, and turbid phantoms and inhomogeneous phantoms to qualitatively illustrate the effects of optical properties and sample geometry on fluorescence spectra. The phantom provides the framework for detailed quantitative investigations of the effects of optical properties, sample size, shape, and structure, boundary conditions, and collection geometry on fluorescence spectra.

Theoretical Study on Fluorescence Spectra of Three Coumarin Derivatives

2013 ◽  
Vol 389 ◽  
pp. 25-28 ◽  
Author(s):  
Ying Wang
Keyword(s):  
Fluorescence Spectra ◽  
Vibrational Analysis ◽  
Emission Spectra ◽  
Dft Method ◽  
Excited Configuration ◽  
Coumarin Derivatives ◽  
Excitation Spectra ◽  
Geometric Configurations ◽  
Td Dft ◽  
Experimental Values

The fluorescence spectra of three coumarin derivatives are studied. Geometric configurations of the three compounds are optimized by DFT method of quantum chemistry on B3LYP/6-31G. There is no imaginary frequency in vibrational analysis. Their excitation spectra are calculated by TD-DFT method. Furthermore, geometric configurations in excited state of the three compounds are optimized by CIS method. Based on the excited configuration emission spectra are also calculated. All the calculated results are in good agreement with experimental values.

scholarly journals Preparation and photoluminescence study of Alumin o-boro silicate YAG fluorescent glass for White LED

2021 ◽  
Author(s):  
Chao Yang ◽  
Guohua Song ◽  
Jianwen Miao ◽  
Tingting Fan
Keyword(s):  
Light Emitting Diode ◽  
Emission Spectra ◽  
Precipitation Method ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Light Emitting ◽  
White Leds ◽  
Near Ultraviolet ◽  
Fluorescence Excitation Spectra ◽  
Co Precipitation

Abstract The YAG: Eu 3+ fluorescent glass for NUV(near ultraviolet) white LEDs was obtained firstly by synthesizing Y 3 Al 5 O 12 (YAG): Eu 3+ precursors through a simple co-precipitation method, and then mixing precursor with B 2 O 3 -Al 2 O 3 -SiO 2 -Na 2 O-BaO glass powder calcined at 1400°C for 2.5 hours. The as-prepared YAG glass-ceramic phosphor was investigated by DTA, XRD, SEM, and photoluminescence (PL). Influence of YAG: Eu 3+ precursor and Eu 3+ doping on excitation and emission spectra also have been studied. The results show that: the phosphor's emission peak located at 393nm is correspond to the 7 F 0 - 5 L 6 transition of Eu 3+ ions, which matches good with UV LED chips; the phosphor gives intense emission at 593nm originating from the 5 D 0 - 7 F 1 transition of Eu 3+ ions. When the YAG precursor is 0.9g and amount of Eu 3+ doped is 0.08, the fluorescence excitation spectra of glass and emission spectra of the peak intensity reach its maximum value. The YAG: Eu 3+ fluorescence glass could be a promising material for the production of near ultraviolet chip white light-emitting diode.

Fluorescence spectroscopy of mechanical pulps III: Effect of chlorite delignification

1995 ◽  
Vol 73 (11) ◽  
pp. 1955-1959 ◽  
Author(s):  
Jennifer A. Olmstead ◽  
Jian H. Zhu ◽  
Derek G. Gray
Keyword(s):  
Fluorescence Spectroscopy ◽  
Fluorescence Intensity ◽  
Fluorescence Spectra ◽  
Lignin Content ◽  
Emission Spectra ◽  
Thermomechanical Pulp ◽  
Fluorescence Excitation ◽  
Lignin Removal ◽  
Mechanical Pulps ◽  
Almost All

Many paper and wood samples fluoresce, but the sources of the emission are not well understood. Fluorescence excitation and emission spectra of paper sheets prepared from thermomechanical pulp (TMP) and bleached chemithermomechanical pulp (BCTMP) showed that the emission from the BCTMP was significantly higher than that from the TMP. Removing almost all of the lignin from both pulps by means of an acid chlorite treatment did not reduce the fluorescence significantly. By means of an approximate correction for changes in sheet reflectivity caused by the chlorite treatment, the fluorescence intensity was found to increase with lignin removal. Clearly, fluorescence is not simply related to lignin content. Keywords: wood pulp, lignin, cellulose, fluorescence spectra, acid chlorite delignification.

FLUORESCENCE EXCITATION SPECTRA OF HUMIC SUBSTANCES

1980 ◽  
Vol 60 (2) ◽  
pp. 373-379 ◽  
Author(s):  
KUNAL GHOSH ◽  
M. SCHNITZER
Keyword(s):  
Free Radical ◽  
Humic Acid ◽  
Ionic Strength ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Fluorescence Excitation Spectra ◽  
Fluorescence Characteristics ◽  
Decreasing Ph ◽  
Radical Content ◽  
Particle Association

Fluorescence excitation spectra of fulvic acid (FA) and humic acid (HA) were recorded at different pH as well as at different netural salt concentrations. Spectra of both FA and HA exhibited distinct bands at 465 nm, while spectra of FA showed additional bands at 360 nm. Fluorescence intensities decreased with decreasing pH and increasing ionic strength. This is due to decreasing ionization, increasing particle association, and to coiling of macromolecular structures. The fluorescence characteristics of FA and HA were observed to be related to the free radical content, color, and phenolic structures. Our data show that fluorescence excitation spectra can be utilized for differentiating between soil FA and HA.

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